1. Field of the Invention
The present invention relates to a sample/hold apparatus and its driving method.
2. Description of the Related Art
A prior art sample/hold apparatus is constructed by a power supply terminal, a ground terminal, an input terminal, an output terminal, a sample/hold terminal, a sampling switching element adapted to pass an input voltage at the input terminal therethrough in response to a sample/hold voltage at the sample/hold terminal, a capacitor having a first terminal connected to an output of the sampling switching element and a second terminal connected to the ground terminal, and a buffer amplifier adapted to perform an impedance conversion upon a voltage at the first terminal of the capacitor to generate an output voltage at the output terminal. The buffer amplifier is powered by a power supply voltage at the power supply terminal and the ground voltage at the ground terminal (see: JP-7-262789-A). This will be explained later in detail.
In the above-described prior art sample/hold apparatus, however, if input voltage Vin has a swing from 0V to VDD, the maximum voltage applied to the capacitor is VDD, so that the breakdown voltage of the capacitor needs to be higher than VDD, which would increase the electrode area thereof. As a result, the above-described prior art sample/hold apparatus would be increased in size.
Particularly, if the above-described prior art sample/hold apparatus is incorporated into an integrated circuit such as a data line driver of a liquid crystal display (LCD) apparatus, including as many sample/hold circuits as the number of data lines, although shrinkage is required, since the electrode area of the capacitor of the sample/hold circuits depending upon the capacitance thereof could not be decreased, the shrinkage, i.e., the enhancement of integration could not be expected.
Generally, note that the occupied area of electrodes of capacitors is about 20 percent in one data line driver. Therefore, in order to enhance of the integration of the data line driver, the decrease of the occupied area of electrodes of such capacitors is indispensable.